How many oxygen atoms are in sodium nitrite?

The molecule TFM is used as a lampricide to control the sea lamprey population in the Great Lakes. It has the formula C7H4NO3F3 (MW = 207.12 g/mol). In one test, it was determined that a concentration of 3.00 mg/L was required to kill 99% of free swimming sea lamprey larvae. How many atoms of fluorine are in 10.0 L of this toxic solution?